Currently, the aluminum electrolysis industry still employs the conventional Hall-Heroult method in which electrolyte always bases on a fundamental system of cryolite-alumina, cryolite generally referring to trisodium hexafluoroaluminate. As trisodium hexafluoroaluminate and alumina are continuously consumed as an aluminum electrolysis process goes on, electrolyte and alumina need to be separately replenished into the fundamental system of electrolyte so as to keep the aluminum electrolysis process continued. Existing electrolyte replenishment system which mainly includes aluminum fluoride and trisodium hexafluoroaluminate consumes much energy as the electrolysis temperature needs to be kept at about 960 degrees centigrade during the whole aluminum electrolysis process for the sake of the high liquidus temperature of an electrolyte and the necessity of keeping a degree of superheat of a certain temperature to keep alumina dissolved relatively well.
Typically, cryolite is industrially prepared using a synthesis method of: reacting anhydrous hydrofluoric acid with aluminum hydroxide to generate fluoaluminic acid, sequentially reacting fluoaluminic acid with sodium hydroxide or potassium hydroxide at a high temperature and filtering, drying, melting and crushing the obtained substances to obtain cryolite; having a molecular ratio m of 3.0, the cryolite synthesized using this method is relatively high in melting point. The molecular ratio m of the cryolite prepared using existing industrial synthesis methods ranges from 2.0 and 3.0, thus, it is difficult to obtain a relatively pure cryolite of low molecular ratio the molecular ratio m of which is 1.0-1.5.
Thus, existing technologies have defects of high energy consumption for electrolysis and dissatisfactory electrolyte and electrolyte replenishment system.